CN107795371B

CN107795371B - Method and system for improving cold start catalyst light-off

Info

Publication number: CN107795371B
Application number: CN201710768781.2A
Authority: CN
Inventors: R·豪斯特; R·A·维德; A·莫雷利
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2016-09-01
Filing date: 2017-08-31
Publication date: 2021-07-16
Anticipated expiration: 2037-08-31
Also published as: DE102017120225A1; RU2017128999A3; US10138781B2; US20180058288A1; RU2696184C2; CN107795371A; RU2017128999A

Abstract

The present disclosure relates to methods and systems for improving cold start catalyst light-off. Methods and systems are provided for accelerating catalyst light-off during engine cold start conditions by inhibiting rotation of a turbocharger shaft. In one example, a method includes inhibiting rotation of a turbocharger shaft during an engine cold start condition until a catalyst is operating at a desired efficiency. Rotation of the shaft may be inhibited via a passive shaft locking mechanism or an active shaft locking mechanism.

Description

Method and system for improving cold start catalyst light-off

Technical Field

The present invention relates generally to methods and systems for controlling a turbocharger of a vehicle engine to accelerate catalyst light-off during engine cold start conditions.

Background

During engine emissions testing, an exhaust catalyst may be required to achieve a desired conversion efficiency within a predetermined time after engine start from cool to ambient conditions. For example, in some engine emissions tests, the exhaust catalyst may be required to operate at greater than 80% efficiency within 20 seconds after engine start-up. Depending on the composition catalyst, the exhaust catalyst operating temperature may begin operating at such efficiencies at temperature conditions ranging from about 800 degrees fahrenheit to 1600 degrees fahrenheit. Therefore, to increase the efficiency of the exhaust catalyst for a short period of time after the engine is started, various operating strategies may be employed to heat the catalyst and accelerate light-off of the exhaust catalyst.

After the engine is started, attempts to address issues related to accelerating light-off of the catalyst may include adjusting a spark timing or air-fuel ratio (AFR) of the engine to increase exhaust gas temperature. However, the present inventors have recognized that while adjusting spark timing and AFR attempts to accelerate catalyst light-off by increasing exhaust temperature, these strategies do not adequately address exhaust heat loss to the exhaust components.

The present inventors have recognized that one source of heat loss from the exhaust gas is due to the increased rate of rotation of the exhaust gas as it travels to the exhaust catalyst. The rate of rotation of the exhaust gas increases downstream of the turbine in an engine including a turbocharger due to the free rotational movement of the turbine. This free rotational movement of the turbine results in an increase in the rotational rate of the exhaust gas as it flows through the turbine to the exhaust catalyst. The increased rotation of the exhaust gas increases the travel time or residence time of the exhaust gas from the exhaust manifold to the exhaust catalyst as the exhaust gas travels axially downstream toward the exhaust catalyst. Therefore, the amount of contact between the exhaust gas and the wall of the exhaust pipe increases, and an increase in the amount of heat loss from the exhaust gas to the exhaust pipe may occur before the exhaust gas reaches the exhaust catalyst.

Disclosure of Invention

In one example, the above-described problem may be solved by a method comprising inhibiting movement (movement) of a shaft of a turbocharger via a shaft locking mechanism in response to an engine cold start condition. The shaft locking mechanism may be a passive shaft locking mechanism or an active shaft locking mechanism. It may be advantageous to use a shaft locking mechanism to control turbocharger rotation rather than relying solely on wastegate position alone. For example, the shaft locking mechanism may be more accurate in controlling the rotational speed of the turbocharger shaft, and/or may have a greater effect on flow rotation than wastegate adjustments. Shaft locking may be provided instead of or in addition to wastegate adjustment, if available.

By suppressing the rotation of the turbocharger, the technical effect of reducing the rotation rate of exhaust gas that spirally passes through the exhaust passage downstream of the turbine of the turbocharger can be achieved, and the heat loss of exhaust gas can be reduced as the exhaust gas travels to the exhaust catalyst. As the exhaust gas travels to the exhaust catalyst, a reduction in heat loss from the exhaust gas may accelerate catalyst light-off and may result in reduced emissions.

As described above, the shaft locking mechanism may be a passive shaft locking mechanism or an active shaft locking mechanism. The passive shaft locking mechanism may include a phase change material that stops or resists rotation of the turbocharger when in a solid state. As the temperature of the phase change material increases, the viscosity of the phase change material may decrease. Once the viscosity of the phase change material decreases below the threshold viscosity, the turbocharger shaft may be enabled to rotate. In some examples, the melting point temperature of the phase change material, as defined by the substance contained in the phase change material, may correspond to a temperature at which the catalyst may operate at a desired efficiency. The passive shaft locking mechanism may facilitate the turbocharger shaft to withstand high temperature conditions without degradation.

The active shaft locking mechanism may include a pin that may be actuated to fit into a recess of the shaft locking mechanism to stop rotation of a shaft of the turbocharger. The active shaft locking mechanism may facilitate quickly stopping or enabling rotation of the turbocharger shaft in response to certain conditions, and changing conditions (such as temperature) that no longer prevent rotation. For example, the shaft rotation may be stopped until precisely when it is desired to enable the shaft to turn. In one example, the active shaft locking mechanism may stop the shaft during a cold engine start condition until a first temperature is reached that reduces exhaust rotation, resulting in accelerated catalyst light-off, but stop during other start conditions or engine restart conditions until a different second (e.g., lower or higher) temperature is reached.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 shows a schematic diagram of an example engine, according to an embodiment of the disclosure.

Fig. 2 shows a first view of the shaft locking mechanism according to the first embodiment.

Fig. 3 shows a second view of the shaft locking mechanism according to the first embodiment.

Fig. 4 shows a cross-sectional view of the shaft locking mechanism according to the first embodiment.

Fig. 5 shows a view of the shaft locking mechanism in the first state according to the second embodiment.

Fig. 6 shows a view of the shaft locking mechanism in the second state according to the second embodiment.

FIG. 7 shows a flowchart of an example method for operating a turbocharger system.

FIG. 8 illustrates a flow chart of an example method for performing mitigation actions of a turbocharger system.

FIG. 9 shows wastegate position, shaft lock, turbine speed, catalyst temperature (T)_CAT) And a graphical representation of an example relationship between engine speeds.

Fig. 2 to 6 are shown approximately to scale.

Detailed Description

The following description relates to systems and methods for improving catalyst light-off during engine cold start conditions in an engine system, such as the engine system of FIG. 1. The shaft locking mechanism (such as described in fig. 2-6) may be operated in locked and unlocked states in response to engine operating conditions such as cold start conditions. In some examples, the shaft locking mechanism may be positioned in a locked state to accelerate catalyst light-off during cold start conditions. The locked state of the shaft lock mechanism can accelerate catalyst light-off by suppressing rotation of the turbine of the turbocharger. Rotation of the turbine may produce rotation in the exhaust flow downstream of the turbine, and such rotation of the exhaust flow may result in heat loss from the exhaust. In other examples, the shaft locking mechanism may be positioned in an unlocked state such that the turbine can be rotated without inhibition. In some examples, the unlocked state may be advantageous to meet engine boost requirements. A controller of the engine system may be executable to execute a routine, such as the routines of fig. 7-8, that controls operation of the turbocharger under conditions where the shaft locking mechanism is operating and under conditions where the shaft locking mechanism may deteriorate. The routine executed by the engine system controller may be based on various relationships of engine components, as depicted in FIG. 9.

Fig. 1-6 illustrate example configurations with relative positioning of various components. If shown as being in direct contact or directly coupled to each other, such elements may be referred to as being in direct contact or directly coupled, respectively, at least in one example. Similarly, elements shown as being proximate or adjacent to each other may be proximate or adjacent to each other, respectively, at least in one example. By way of example, components placed in coplanar contact with each other are referred to as coplanar contacts. As another example, in at least one example, these elements, located apart from each other with only space in between and no other components, may be referred to as above. As yet another example, elements shown above/below each other, on opposite sides of each other, or on left/right sides of each other may be referred to above with respect to each other. Further, as shown, in at least one example, the topmost element or the topmost point of an element may be referred to as the "top" of the component, and the bottommost element or the bottommost point of an element may be referred to as the "bottom" of the component. As used herein, top/bottom, upper/lower, above/below may be with respect to a vertical axis of the figures, and are used to describe the positioning of elements in the figures with respect to each other. Thus, in one example, an element shown as being above other elements is positioned vertically above the other elements. As another example, the shapes of elements depicted in the figures may be referred to as having those shapes (e.g., such as being annular, straight, planar, curved, rounded, chamfered, angled, etc.). Further, in at least one example, elements shown as intersecting one another may be referred to as intersecting elements or as intersecting one another. Further, in one example, an element shown as being within another element or shown as being external to another element may be referred to above.

Referring to FIG. 1, an internal combustion engine 10 including a plurality of cylinders, one cylinder of which is shown in FIG. 1, is controlled by an electronic engine controller 12. Engine 10 includes combustion chamber 30 and cylinder walls 32 with piston 36 positioned therein and connected to crankshaft 40. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57.

Fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Alternatively, fuel may be injected into the intake port, which is known to those skilled in the art as port injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown).

Further, intake manifold 44 is shown in communication with turbocharger compressor 162. Shaft 161 mechanically couples turbocharger turbine 164 to turbocharger compressor 162. The exhaust rotary turbine 164 is coupled to the compressor 162 via a shaft 161. However, in some examples, the wastegate 172 may allow exhaust gas to bypass the turbine 164 by redirecting the exhaust gas through the turbine bypass conduit 174. When the turbine and the compressor of the turbocharger are coupled via shaft 161, rotation of turbine 164 may cause compressor 162 to rotate. As compressor 162 rotates, compressor 162 may draw air from air intake 42 to supply intake plenum 46. However, in some examples, compressor bypass valve 165 may redirect intake air through compressor bypass conduit 168. In some examples, turbine bypass conduit 174 and compressor bypass conduit 168 may be used to control the rotational speed of turbine shaft 161 in combination with shaft locking mechanism 166. However, in other embodiments, compressor bypass conduit 168 and turbine bypass conduit 174 may not be provided.

The turbocharger compressor 162, shaft 161, turbine 164, and shaft locking mechanism 166 may be part of a turbocharger system. The turbocharger system may be a separate component mounted to the exhaust component of the engine, and the turbocharger system may be contained within a turbocharger housing. Different types of turbocharger systems may be possible. For example, a single-spool turbocharger system or a twin-spool turbocharger system may be possible.

The rotation of the shaft 161 may be supported by a first bearing 176 and a second bearing 178. The

bearings

176 and 178 that rotatably support the shaft 161 may be high speed bearings. In one example, for example, bearing 176 may surround shaft 161 and may be positioned between turbocharger compressor 162 and shaft locking mechanism 166. The bearing 178 may surround the shaft 161 and may be positioned between the turbocharger turbine 164 and the shaft locking mechanism 166. Although

bearings

176 and 178 are shown positioned at either end of the shaft, other positioning may be possible, and additional bearings may be possible, to provide further support for rotation of the shaft 161.

Several different types of bearing arrangements may be possible to rotatably support the shaft 161. For example, the

bearings

176 and 178 may be a semi-floating journal (journal) bearing with oil squeeze film (oil hydraulic film), a full floating journal bearing with oil squeeze film, a ball bearing with oil coating pressed on the shaft 261, a ball bearing with sealing grease pressed on the shaft 261, a needle bearing, or an air bearing. In example bearings using oil coatings or sealing grease, the oil coating or sealing grease provides lubrication to the bearings to prevent degradation of the bearings and the turbocharger shaft 161.

The shaft 161 includes a shaft locking mechanism 166. In some examples, the shaft locking mechanism 166 may be in communication with the controller 12. The shaft locking mechanism 166 may inhibit rotation of the shaft 161 in response to engine operating conditions. For example, in response to engine operating conditions, controller 12 may actuate an actuator of shaft locking mechanism 166 to inhibit rotation of shaft 161 or to enable rotation of shaft 161. In other examples, the shaft locking mechanism 166 may inhibit rotation of the shaft 161 or enable rotation of the shaft 161 in response to the diagnostic test results. In other embodiments, the shaft locking mechanism 166 may not be in communication with the controller 12.

Optional electronic throttle 62 adjusts the position of throttle plate 64 to control the flow of air from intake 42 to compressor 162 and intake manifold 44. In one example, a high pressure dual stage fuel system may be used to generate higher fuel pressures. In some examples, throttle 62 and throttle plate 64 may be positioned between intake valve 52 and intake manifold 44 such that throttle 62 is a port throttle.

Distributorless ignition system 88 provides ignition spark to combustion chamber 30 via spark plug 92 in response to controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled to exhaust manifold 48 upstream of catalytic converter 70. Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor 126.

In one example, converter 70 may include a plurality of catalyst bricks. In another example, multiple emission control devices, each having multiple bricks, may be used. In one example, converter 70 may be a three-way type catalyst. Throughout this disclosure, it will be understood that reference to a catalyst refers to an exhaust catalyst, such as is included in converter 70. The converter 70 may be coupled downstream of the turbocharger turbine 164, and exhaust gas traveling from the exhaust manifold 48 may pass through the turbine 164 before reaching the converter 70. In examples where wastegate 172 and turbine bypass conduit 174 are included in the engine system in addition to the turbocharger, converter 70 may be coupled downstream of both turbocharger turbine 164 and turbine bypass conduit 174. Further, in examples that include a wastegate 172 and a turbine bypass conduit 174 in addition to the turbocharger turbine 164, exhaust gas traveling from the exhaust manifold 48 may first pass through the turbine bypass conduit 174 and/or the turbine 164 before traveling through the converter 70.

The controller 12 is shown in fig. 1 as a conventional microcomputer including: microprocessor unit 102, input/output ports 104, read only memory 106 (e.g., non-transitory memory), random access memory 108, non-volatile memory 110, and a conventional data bus. The controller 12 may be part of a control system 14. The control system 14 may further include sensors 16 and actuators 18 (various examples of which are described herein). In addition to those signals previously discussed, controller 12 of control system 14 is also shown receiving various signals from sensors 18 coupled to engine 10, including: engine Coolant Temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; a position sensor 134 coupled to the accelerator pedal 130 for sensing force applied by the foot 132; the pressure sensor may be coupled to the oil pump to determine a pressure of the oil pump (not shown); a position sensor 154 coupled to the brake pedal 150 for sensing the force applied by the foot 152; a measurement of engine manifold pressure (MAP) from pressure sensor 122 coupled to intake manifold 44; measurements of turbine inlet gas pressure and/or exhaust pressure may be measured from a pressure sensor coupled near turbine 164; an engine position sensor from a Hall effect sensor 118 sensing crankshaft 40 position; a measurement of air mass entering the engine from sensor 120; and measurements of throttle position from sensor 58; a measurement of turbine inlet gas pressure may be inferred from a pressure sensor coupled in the exhaust manifold. Atmospheric pressure may also be sensed (sensor not shown) for processing by controller 12. The engine position sensor 118 may generate a predetermined number of equally spaced pulses per revolution of the crankshaft from which engine speed (RPM) may be determined. The shaft position sensor may sense the rotational speed of the shaft 161. Further, in some embodiments, the controller 12 may receive a signal from a sensor of the shaft locking mechanism 166. For example, controller 12 may receive a signal from a position sensor of shaft locking mechanism 166. These position sensors may sense the position of the actuator of the shaft locking mechanism 166 or the pin of the shaft locking mechanism 166. In some examples, the shaft locking mechanism 166 may also have a temperature sensor positioned therein. In other examples, the temperature of the shaft locking mechanism 166 may be based on one or more of ECT, the output of a temperature sensor coupled to the catalytic converter 70, or the output of a temperature sensor positioned in the exhaust passage 48. Position sensors may also be coupled to one or both of compressor bypass valve 170 and wastegate 172 to provide signals to controller 12 of their positions.

The controller 12 of the control system 14 receives signals from the various sensors 16 of FIG. 1 and employs the various actuators 18 of FIG. 1 to adjust engine operation based on the received signals and instructions stored on the memory of the controller 12. For example, the adjustment shaft locking mechanism may include an actuator for a pin of the adjustment shaft locking mechanism. In another example, adjusting the position of the wastegate 172 may include adjusting an actuator of the wastegate 172.

In some examples, the engine may be coupled to a motor/battery system in a hybrid vehicle. Further, in some examples, other engine configurations may be employed, such as a diesel engine.

During operation, each cylinder within engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Generally, during the intake stroke, exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44 and piston 36 moves to the bottom of the cylinder to increase the volume within combustion chamber 30. Piston 36 is near the bottom of the cylinder and at a position at the end of its stroke (e.g., when combustion chamber 30 is at its largest volume) typically referred to by those skilled in the art as Bottom Dead Center (BDC). During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is commonly referred to by those skilled in the art as Top Dead Center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by a known ignition device, such as spark plug 92, resulting in combustion. During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts piston motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48 and the piston returns to TDC. Note that the above is presented as an example only, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, retarded intake valve closing, or various other examples.

For purposes of discussion, fig. 2-4 are described collectively. Fig. 2 to 4 show various views of the shaft locking mechanism according to the first embodiment. Similar components introduced in the first drawing may be similarly numbered in subsequent drawings rather than being reintroduced.

Fig. 2 shows a first view of a shaft locking mechanism 200 according to a first embodiment. The shaft locking mechanism 200 may correspond to the shaft locking mechanism 166 described in fig. 1. The shaft locking mechanism 200 may be a passive shaft locking mechanism of a turbocharger system and may include an outer housing 202 surrounding at least a portion of a shaft 261 of the turbocharger system. In some examples, the shaft 261 may correspond to the shaft 161 depicted in fig. 1. Although not shown, the shaft 261 may be rotationally coupled to a compressor at the first end 208 of the shaft and to a turbine at the second end 210 of the shaft. The shaft 261 may be rotatably supported via

bearings

176 and 178 described with respect to fig. 1. Further, although the shaft locking mechanism 200 is shown positioned approximately halfway between the first end 208 and the second end 210 of the shaft 261, other positioning of the shaft locking mechanism may be possible. For example, the shaft locking mechanism 200 may be positioned to contact a rear disk (back disk) of a turbocharger wheel of a turbocharger, where the rear disk is a substantially flat planar side of the turbine 164 or compressor 162 including blades opposite a side of the turbine 164. In another example, the shaft locking mechanism 200 may be positioned to contact a rotating vane segment structure. Different arrangements of the shaft locking mechanism may facilitate packaging constraints for different turbocharger systems.

The outer housing 202 may surround a portion of the shaft 261, and the portion of the shaft 261 surrounded by the outer housing 202 may include a plurality of recesses (recoss) or slots 204. The outer housing 202 may be fixed to a portion of the engine such that the shaft 261 may rotate relative to the outer housing 202. In other words, the outer housing 202 may be fixed to a portion of the engine such that the shaft 261 may rotate within the outer housing 202. In some examples, the outer housing 202 may be secured to an interior of a housing of the turbocharger system, where the outer housing 202 is surrounded by the turbocharger housing. For example, the turbocharger housing may surround the shaft 261, the shaft locking mechanism 200, the turbine 164, and the compressor 162, and the turbocharger housing may be mounted to the engine.

The recess 204 may be integral to the shaft 261, and the recess 204 may be recessed relative to a base surface of the shaft 261. A closed cavity may be formed between the shaft 261 and the recess 204 and the outer housing 202. In other words, a cavity may exist between the shaft 261 and the recess 204 and outer housing 202 integrally formed therewith. The cavity may be filled with a phase change material. In some examples, the phase change material may be a wax, such as wax particles. The phase change material may surround the shaft 261 and may be located within a recess 204 of the shaft 261 between an exterior surface of the shaft 261 and an interior surface of the outer housing 202.

In some examples, the shaft locking mechanism 200 may directly contact the shaft 261. In examples where shaft locking mechanism 200 directly contacts shaft 261, shaft locking mechanism 200 may be referred to as a directly coupled shaft locking mechanism. In other words, in examples where shaft locking mechanism 200 contacts shaft 261 to couple shaft 261 and shaft locking mechanism 200 without other components positioned therebetween, the shaft locking mechanism may be referred to as a directly coupled shaft locking mechanism.

In other examples, the shaft locking mechanism 200 may not directly contact the shaft 161 and, instead, may be indirectly coupled to the shaft 161. In examples where the shaft locking mechanism 200 is indirectly coupled to the shaft 261, the shaft locking mechanism 200 may be coupled to a bearing that rotatably supports the shaft 261. For example, the shaft locking mechanism 200 may be coupled to the

bearings

176 and 178 described with respect to fig. 1 via the ring structure 206 and directly contact the

bearings

176 and 178. In some examples, the shaft locking mechanism 200 may be directly coupled to the rotating portions of the bearings 176 and 178 (i.e., the inner race of the bearings if the bearings are cartridge type bearings).

The ring structure 206 may rotatably support the outer housing 202 such that the shaft 261 may rotate within the outer housing 202. In some examples, the ring structure 206 may be a bearing. The ring structure 206 may be positioned between the outer housing 202 and the shaft 261, and the portion of the shaft locking mechanism 200 including the recess 204 may be positioned between the ring structure 206. The annular structure 206 may directly or indirectly couple the outer housing 202 to the shaft 261. More specifically, the ring structure 206 may rotationally couple the outer housing 202 to the shaft 261, and the shaft 261 may rotate relative to the housing 202. Additionally, the annular structure 206 may form a seal between the outer housing 202 and the shaft 261. The seal formed by annular structure 206 may contain the phase change material in a cavity enclosed by outer housing 202 when the phase change material melts.

In some examples, the phase change material may inhibit rotation of the shaft 261. For example, the phase change material may be in a solid phase within the recess 204 and against (against) an inner surface of the outer housing 202, coupling the shaft 261 to the outer housing 202 and preventing rotation of the shaft 261. The phase change material may solidify in response to a condition in which the phase change material may be below a threshold temperature. Thus, even if the exhaust gas flows through the turbine to which the shaft 261 is attached, rotation of the shaft 261 may be inhibited, and in some examples, rotation may be stopped if the phase change material is below a threshold temperature. Dampening the movement of the shaft 261 may facilitate reducing exhaust heat loss downstream of the turbocharger turbine during engine cold starts by reducing or preventing spiraling of the exhaust downstream of the turbine. Reducing heat loss from the exhaust gas downstream of the turbocharger turbine during engine cold starts may accelerate catalyst light-off, resulting in reduced vehicle emissions.

The phase-change material may decrease in viscosity in response to an increase in temperature of the phase-change material. As the exhaust gas travels from the exhaust manifold to the catalyst, the exhaust gas may increase the temperature of the phase change material via heat transferred to the shaft 261. In addition, ambient temperature may also increase the temperature of the phase change material. As the temperature of the phase change material within the cavity enclosed by the outer housing 202 increases, the phase change material within the cavity may begin to change from a solid phase to a liquid phase (i.e., melt). As the temperature of the phase change material increases, the phase change material may become less viscous. This increase in the temperature of the phase change material may be in response to the engine's exhaust heating the shaft 261. Heat from the shaft 261 may then be transferred to the phase change material, thereby increasing the temperature of the phase change material. As the viscosity of the phase change material decreases, the rotational resistance of the shaft 261 decreases, and the shaft 261 may begin to rotate in response to the viscosity decreasing below a threshold viscosity.

In one example, the viscosity of the phase change material may decrease below a threshold viscosity in response to the phase change material being greater than a threshold temperature, and the shaft 261 may be enabled to rotate in response to the phase change material being less than the threshold viscosity. For example, the threshold temperature may be a melting point of the phase change material. In some examples, the phase change material filling the cavity of the shaft locking mechanism including the recess 204 may have a melting point temperature that is approximately the same as the catalyst light-off temperature. However, in other examples, the temperature of the phase change material may correspond to a temperature at which the catalyst may operate at a desired efficiency.

A threshold temperature of the phase change material that is approximately the same temperature at which the catalyst is light off or approximately the same temperature at which the catalyst may operate at a desired efficiency may have several advantages. For example, if the threshold temperature of the phase change material is approximately the same as the temperature at which the catalyst ignites, the phase change material may inhibit rotation of the shaft 261 until catalyst light-off occurs, where inhibiting rotation of the shaft 261 includes stopping rotation of the shaft 261. Inhibiting rotation of the shaft 261 until catalyst light-off occurs may reduce heat loss from the exhaust gas to the exhaust component, thereby accelerating the catalyst heating to the light-off temperature. Similarly, if the threshold temperature of the phase change material is approximately the same as the temperature at which the catalyst operates at the desired efficiency, the phase change material may inhibit rotation of the shaft 261 until the catalyst reaches a temperature at which the catalyst operates at the desired efficiency, wherein inhibiting rotation of the shaft 261 includes stopping rotation of the shaft 261. Inhibiting rotation of the shaft 261 until the catalyst reaches a temperature at which the catalyst operates at a desired efficiency may accelerate heating of the catalyst to the desired efficiency.

Fig. 3 shows a second view of the shaft locking mechanism 200 according to the first embodiment. The second view of the shaft locking mechanism 200 according to the first embodiment is shown without an external housing to better view some features of the shaft locking mechanism 200. For example, the ring-shaped structure 206 and the recess 204 may be more easily observed in the second view provided in fig. 3.

As previously described, the ring structure 206 may rotatably support the outer housing of the shaft locking mechanism. The ring structure 206 may be raised (raised) relative to a base surface of the shaft 261, and the ring structure 206 may surround the shaft 261. The ring structure 206 may be at the first and second ends of the shaft locking mechanism 200, with a portion of the shaft locking mechanism 200 including the recess 204 positioned between the first and second ends of the shaft locking mechanism.

The recess 204 positioned between the first and second ends of the shaft locking mechanism may be recessed relative to the base surface of the shaft 261. In some examples, the cross-section of the recess 204 may be rectangular. However, other cross-sectional shapes may also be possible. For example, the cross-section of the recess 204 may be circular or triangular. The recess 204 may form a cavity that the phase change material may fill. In some examples, the recesses 204 may be equally spaced around the shaft 261, and the size and shape of the recesses 204 may be uniform. However, other arrangements of the recesses 204 may be possible. For example, the spacing of the recesses 204 around the shaft 261 may vary, or the dimensions of the recesses may be non-uniform.

Fig. 4 shows a third view of the shaft locking mechanism 200 according to the first embodiment, wherein the third view is a cross-sectional view. The cross-sectional view may enable a better view of the cavity between the outer housing and the base surface and recess of the shaft. The cavity 406, which may be filled with a phase change material as discussed above, is enclosed by the outer housing 202. In particular, the cavity 406 is enclosed between the inner surface 402 of the outer housing 202 and the base surface 404 and the recess 204 of the shaft locking mechanism 200.

For purposes of discussion, fig. 5 and 6 will be described collectively. Components in fig. 6 that are similar to components described in fig. 5 may be similarly labeled and are not reintroduced in the description of fig. 6.

Fig. 5 shows the shaft locking mechanism 500 in the first state according to the second embodiment. The first state shown is an unlocked state of the shaft locking mechanism 500. The shaft locking mechanism 500 may be an actively (activery) controlled shaft locking mechanism and may be controlled via the control system 14. Control system 14 may include sensors 16, controller 12, and actuators 518, and control system 14 may correspond to the control system described in fig. 1. For example, the sensor 16 and controller 12 may correspond to the sensors and controllers described in fig. 1. The actuator 518 is an actuator for the pin 508 of the shaft locking mechanism 500 and may be one of the actuators 18 described with respect to fig. 1.

The shaft locking mechanism 500 may share similar features with the shaft locking mechanism 200 described in fig. 2-4. For example, the shaft locking mechanism 500 may include an annular structure 506 that corresponds to the annular structure 206 of the shaft locking mechanism 200. Further, the shaft locking mechanism 500 may include a plurality of recesses 504 corresponding to the recesses 204 of the shaft locking mechanism. Further, shaft locking mechanism 500 may include a shaft 561 that corresponds to shaft 261 described with respect to shaft locking mechanism 200. Descriptions of similar features highlighted between the shaft locking mechanism 500 and the shaft locking mechanism 200 (e.g., the ring feature 506, the recess 504, and the shaft 561) may be shared. For example, the descriptions of the ring feature 206, the recess 204, and the shaft 261 in fig. 2-4 may apply to the ring feature 506, the recess 504, and the shaft 561, respectively, of the shaft locking mechanism 500 described in fig. 5-6. Further, the shaft 561 described with respect to fig. 5 and 6 may also be supported by the

bearings

176 and 178 described in fig. 1 and 2 to 4. It should be noted, however, that the description of the ring features, bearings (i.e., bearings 176 and 178), recesses, and shafts described with respect to the outer housing in fig. 2-4 does not apply to these features in fig. 5-6, since the shaft locking mechanism 500 does not include an outer housing. Further, it should be noted that with the shaft locking mechanism 500, the bearings may be sealed within the bearing cavities to separate the oil, sealed grease, or air mixture of the bearings from the pins 508 and the actuators 518 of the shaft locking mechanism 500. In some examples, a lubricant (e.g., oil, sealed grease, or air) that seals the bearings may be beneficial to prevent degradation of the pin 508 and the actuator 518.

As described above, the shaft locking mechanism 500 may be actively controlled via the control system 14. In one example, the control system 14 may receive signals from the sensors 16, and the controller may then actuate the actuators 518 in response to the signals received from the sensors 16. The sensor 16 may be any of the sensors described with respect to fig. 1. For example, the sensor may be a sensor that detects engine operating conditions. In some examples, the sensor 16 detects a condition, such as engine speed, catalyst temperature, rotational speed of a turbocharger shaft, temperature of a shaft locking mechanism, exhaust pressure, or turbine inlet pressure, or position of the pin 508 of the shaft locking mechanism 500.

In some examples, one or more of the sensors 16 may be position sensors positioned on one or more of the shaft 561, the pin 508, and the actuator 518 of the shaft locking mechanism 500. The position of the shaft 561 may be based on the rotational speed of the shaft, while the positions of the pin 508 and the actuator 518 may correspond to whether the pin 508 and the actuator 518 are in a position that will lock or unlock the shaft locking mechanism. Position sensors positioned on one or more of the pins 508, the shaft 561, and the actuator 518 may detect the positions of these components of the shaft locking mechanism 500 and may generate outputs indicative of these positions to the controller 12. In some examples, one position sensor may be used to detect the position of more than one of the pin 508, shaft 561, and actuator 518. For example, a position sensor positioned on the actuator 518 may detect the position of the pin 508 and the rotational speed of the shaft 561. Other examples may also be possible in which one position sensor may be used to detect the position of more than one component. Based on the position of one or more of the shaft 561, pin 508, and actuator 518, the state of the shaft locking mechanism 500 may be determined.

The actuator 518 may be an actuator for the pin 508 of the shaft locking mechanism 500. In some examples, the actuator 518 may be a solenoid actuator. However, in other examples, the actuator 518 may be a motor and gear actuator or a roller and pin actuator. The actuator 518 may control the position of the pin 508, wherein a first position of the pin 508 may unlock the shaft locking mechanism 500 and a second position of the pin 508 may lock the shaft locking mechanism.

The pin 508 is a structure that can fit within one of the recesses 504. In some examples, the pin 508 may be rectangular in shape. However, other shapes are possible. The pin 508 may fit within one of the recesses 504 such that at least a portion of the pin 508 may be surrounded by the recess 504. The pin 508 may be positioned within one of the recesses 504 via an actuator 518.

In some examples, the recesses 504 of the shaft locking mechanism 500 may be arranged with less than a threshold distance between each recess 504 to more easily align the pin 508 with one of the recesses 504. For example, the threshold distance between each recess 504 may be a distance requiring less than a maximum of 45 degrees of rotation of the shaft 561 in order to align one of the recesses 504 with the pin 508. The pin 508 and the recess 504 may be aligned when the actuator 518 may position the pin 508 within the recess 504 without any additional rotation of the shaft 561. Thus, spacing recesses 504 less than a threshold distance apart may facilitate faster positioning of pin 508 within one of recesses 504, as aligning pin 508 and one of recesses 504 requires less rotation of shaft 561.

In some examples, in response to a request that the shaft locking mechanism 500 be in a locked state, the actuator 518 may advance the position of the pin 508 toward the shaft 561 regardless of the alignment of the pin 508 and the recess 504. In other words, the actuator 518 advances the position of the pin 508 toward the shaft 561 in response to a request that the shaft locking mechanism 500 be in a locked state, regardless of whether the pin 508 is aligned with one of the recesses 504 or whether the pin 508 is aligned with a shaft base surface located between the recesses 504. If the pin 508 is not aligned with one of the recesses 504 when the actuator 518 advances the position of the pin 508 toward the shaft 561, the pin 508 may contact the base surface of the shaft 561 between the two recesses 504. If the position of the pin 508 is advanced and the pin 508 comes into contact with the base surface of the shaft 561, rather than being positioned within one of the recesses 504, the position of the pin 508 can be adjusted to enable the shaft 561 to rotate until the pin 508 is aligned with one of the recesses 504. Then, when the pin 508 is aligned with one of the recesses 504, the actuator 518 may adjust the position of the pin 508 such that the pin 508 may be positioned such that at least a portion of the pin is completely surrounded by the recess 504. However, in other examples, the actuator 518 may not advance the position of the pin 508 relative to the shaft 561 until the pin 508 is aligned with the recess 504. The alignment of the pin 508 with the recess 504 may be determined based on the position sensor output of one or more of the shaft 561, the pin 508, and the actuator 518.

Controlling the position of the pin 508 may include pulling back (retracting) the pin 508 via the actuator 518 to disengage the pin 508 from one of the recesses 504. In this disengaged position, none of the recesses 504 may encompass any portion of the pin 508. In examples where the pin 508 is in the disengaged position, the shaft 561 may rotate without being inhibited by the shaft locking mechanism 500. Thus, when the shaft locking mechanism is in the unlocked state, the position of pin 508 may include a position where pin 508 is disengaged from recess 504. As shown in fig. 5, the shaft locking mechanism 500 is shown disengaged or in a pulled back position relative to the recess 504 when the shaft locking mechanism is in an unlocked state. Controlling the position of the pin 508 may also include positioning the pin 508 to engage one of the recesses 504, which will be discussed in more detail later.

Fig. 6 shows the shaft locking mechanism 500 in a second state according to the second embodiment. The second state may be a locked state of the shaft locking mechanism.

The shaft locking mechanism 500 may be transitioned to the locked state via controlling the position of the pin 508. Controlling the position of the pin 508 such that the shaft locking mechanism 500 is in the locked state may include advancing the position of the pin 508 such that the pin 508 may engage with one of the recesses 504. The pin 508 may be engaged with one of the recesses 504 by positioning the pin 508 via the actuator 518 to insert the pin 508 into one of the recesses 504. When the pin 508 is at least partially surrounded by one of the recesses 504, the pin 508 may engage one of the recesses 504. Engagement of the pin 508 with one of the recesses 504 may stop (i.e., inhibit) rotation of the shaft 561. The shaft 561 may not rotate when stopped by engagement of the pin 508 with one of the recesses 504. Thus, the second state of locking the pin 508 of the shaft lock mechanism 500 may include advancing the position of the pin 508 toward the shaft 561 to engage the pin 508 with one of the recesses 504.

During conditions when the catalyst may be below the threshold temperature, it may be advantageous for the locating pin 508 to not rotate the shaft 561. For example, in response to the catalyst temperature being below the threshold temperature, rotation of the shaft 561 may be prevented (i.e., stopped) because preventing rotation of the shaft 561 may reduce heat loss from the exhaust gas downstream of the turbine of the turbocharger and accelerate heating of the catalyst, resulting in reduced emissions.

Referring now to FIG. 7, an example flow chart of a method 700 for operating a turbocharger system is shown. The instructions for performing method 700 and the remaining methods included herein may be executed by the controller based on instructions stored on a memory of the controller in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to fig. 1-6. The controller may employ actuators of the engine system (including actuators of the turbocharger system) to adjust engine operation according to the method described below. Moreover, the numerical identifiers previously introduced in fig. 1-6 are similarly numbered for discussion purposes and are not re-introduced in the description of method 700 and the remaining methods included herein.

Method 700 may begin at 701. In some examples, method 700 may be initiated in response to a threshold period of time being exceeded since method 700 last exited. At 702, engine operating conditions are determined. Engine operating conditions may include, but are not limited to, temperature of the engine, atmospheric temperature and pressure, engine speed, engine load, time since engine start, number of combustion events since engine start, intake manifold pressure, desired engine torque, engine load, boost pressure, turbocharger shaft rotational speed, and throttle position. Other engine operating conditions may also include turbine inlet gas pressure or exhaust pressure, measured or inferred. In examples where one or more of the turbine inlet gas pressure and exhaust pressure are measured, the pressure may be measured via a pressure sensor located near the turbocharger turbine. In examples where one or more of turbine inlet gas pressure and exhaust pressure are inferred, the pressure may be inferred based on a temperature of the exhaust gas or based on a pressure sensor coupled to the exhaust manifold, for example. Other ways to infer turbine inlet pressure and exhaust pressure may be possible, and may take into account one or more of various temperature measurements, such as ECT or temperature sensor output throughout the engine, air flow rate, and various pressure measurements taken throughout the engine. Method 700 proceeds to 704 after engine operating conditions are determined.

At 704, method 700 determines a desired state of the shaft locking mechanism. The desired state of the shaft locking mechanism may include one of an unlocked state and a locked state. The desired state of the shaft locking mechanism may be a locked state responsive to a locked state condition. These lock-up condition conditions may include one or more of an engine cold start condition, an engine boost condition exceeding a desired engine boost threshold, and an engine off condition. The desired state of the shaft locking mechanism may be an unlocked state responsive to an unlocked state condition. These unlocked state conditions may include one or more of complete engine warm-up and an override (override) condition.

In one example, in an example where the desired state of the axle locking mechanism is determined to be a locked state in response to an engine cold start condition, the engine cold start condition may include an engine temperature less than a threshold temperature. For example, the engine temperature may be estimated based on the coolant temperature. The engine cold start condition may additionally or alternatively include a condition in which a number of combustion events since the engine start and before a next engine off condition is less than a threshold number of combustion events, wherein there is no engine off condition between the engine start and the next engine off condition. Further, the engine cold start condition may additionally or alternatively include a condition wherein a period of time since the engine start and before a next engine off condition is less than a threshold period of time, wherein there is no engine off condition between the engine start and the next engine off condition. In some examples, the engine cold start condition may additionally or alternatively include where the engine is started after a period of time that exceeds a threshold period of time since a last engine combustion event.

The cold start condition may also include a condition in which the catalyst temperature is below a threshold temperature. For example, the threshold temperature may be a light-off temperature of the catalyst. In other examples, the threshold temperature may be a temperature at which the catalyst operates at a desired efficiency. Locking the shaft locking mechanism to inhibit movement of the shaft may facilitate reducing heat loss downstream of the turbocharger turbine during engine cold starts, thereby accelerating catalyst heating.

In examples where the desired state of the shaft locking mechanism is determined to be a locked state in response to the engine boost condition exceeding the desired boost level, locking the shaft may quickly reduce the boost level in the engine to the desired boost level. This may be advantageous to prevent problems (such as knocking). In some examples, the shaft may be locked in conjunction with controlling the wastegate to an open state if the engine boost condition exceeds the desired boost condition. Opening the wastegate when the shaft locking mechanism is in the locked state may reduce an amount of pressure applied to the pin of the shaft locking mechanism when the shaft locking mechanism is in the locked state. Reducing the amount of pressure applied to the pin of the shaft locking mechanism may prevent degradation of the shaft locking mechanism.

In examples where the desired state of the shaft locking mechanism is determined to be the locked state in response to an engine off condition, the pin of the shaft locking mechanism may be moved to the engaged position immediately after the engine off condition is determined. However, in other examples, the pin may be in the engaged position such that the shaft locking mechanism is in the locked state in response to the rotational speed of the turbocharger shaft decreasing below a threshold speed after an engine off condition or in response to a period of time exceeding a threshold time period after an engine off condition. In some examples, the threshold speed of the turbocharger shaft may be a speed when rotation of the turbocharger shaft is stopped. In other examples, the threshold speed of the turbocharger shaft may be a speed that determines that a pin of the shaft locking mechanism may be actuated while reducing the risk of damage to the pin.

In some examples, even if the desired state of the shaft locking mechanism is a locked state in response to one or more of the above locked state conditions, the desired locked state may be overridden in response to one or more of the override conditions. In other words, even if a locked state condition exists, the desired state of the axle locking mechanism may be an unlocked state in response to an override condition. These override conditions may include one or more of turbine inlet gas pressure exceeding a threshold, exhaust gas pressure exceeding a threshold pressure, accelerator pedal-in events, engine boost requirements exceeding a threshold, detection of traffic conditions requiring high speeds, environmental conditions that degrade engine performance, and engine load exceeding a threshold load. Overriding the desired shaft locking mechanism state from the locked state to the unlocked state in response to these override conditions may be beneficial to avoid degradation of engine performance.

In examples where the override condition being present is turbine inlet gas pressure or exhaust pressure being greater than a threshold, the threshold pressure may be a predetermined pressure at which damage to the shaft locking mechanism may occur. In one example, the threshold pressure may be a predetermined pressure that determines that one or more of the pin and the actuator may be degraded. The rotational force on the shaft and hence the load applied to the locking mechanism is directly proportional to the turbine inlet gas pressure. Thus, when determining the desired locked position state, it is beneficial to ensure that there is a threshold value for this pressure that is referenced. In this way, the system may please resolve the lock shaft when the turbine inlet pressure exceeds a certain threshold that provides protection against lock mechanism damage and shaft damage.

As another example, even if a locked condition exists, the desired state may be overridden from the locked state to the unlocked state in response to the presence of an accelerator pedal oil feed override condition. As a more specific example, if an engine cold start condition exists and the shaft locking mechanism is in a locked state, the shaft lock may be overridden to an unlocked position in response to an accelerator oil feed event during engine start.

In another example, even in a locked state condition, if the engine boost demand exceeds a threshold boost demand, the desired state may be overridden to an unlocked state. In another example, the desired state of the axle locking mechanism may be overridden from the locked state to the unlocked state in response to a traffic condition that requires the vehicle to travel at a high speed (such as highway speed). In some examples, these traffic conditions may be detected through C2C or C2X communications. In other examples, traffic conditions may be determined via GPS navigation data and wirelessly accessed traffic information. Environmental conditions that may degrade engine performance may include low air density conditions (e.g., due to high altitude). These environmental conditions may be determined in response to GPS navigation data. Finally, during a locked state condition, a desired state of the shaft locking mechanism may be overridden from a locked state to an unlocked state in response to the engine load exceeding a threshold engine load.

In response to one or more of the above override conditions existing during the locked state, the desired state of the shaft locking mechanism may be overridden from the locked state to the unlocked state. Overriding the desired state of the axle locking mechanism may cause the axle locking mechanism to transition from the locked state to the unlocked state even during engine cold start conditions. In other words, even during a locked state condition where shaft movement would normally be inhibited, the desired state may be overridden and shaft movement may be enabled in response to one or more override conditions. For example, the shaft locking mechanism may be in a locked state and inhibit movement of the shaft during one or more locked state conditions, and then in response to one or more override conditions and during the locked state conditions, the shaft locking mechanism state may be transitioned to an unlocked state and movement of the shaft may be enabled. In some examples, transitioning the shaft locking mechanism from the locked state to the unlocked state may result in rotation of the turbocharger turbine in response to an override condition before the catalyst temperature meets one or more of a threshold temperature, the engine temperature reaches a temperature threshold, and a threshold number of combustion events since the engine start occurred.

For an example where the desired state of the shaft locking mechanism is determined to be the unlocked state in response to completion of engine warm-up, engine warm-up completion may be determined in response to a catalyst temperature being greater than a threshold temperature, which may be a light-off temperature of the catalyst. In other examples, the threshold temperature may be a temperature at which the catalyst operates at a desired efficiency.

As another example, completion of warm-up of the engine may additionally or alternatively be determined in response to a number of combustion events since engine start greater than a threshold number of combustion events, where the number of combustion events may be since engine start and before a next engine off condition.

As another example, completion of warm-up of the engine may additionally or alternatively be determined in response to a period of time since engine start being greater than a threshold period of time, wherein the period of time since engine start precedes a next engine off condition, wherein there is no engine off condition between the engine start and the next engine off condition.

In response to a determination that sufficient oil flow is available for bearings of the turbocharger, it may additionally or alternatively be determined that warm-up of the engine is complete. For example, in response to the viscosity of the turbocharger bearing oil being less than a threshold viscosity, a sufficient oil flow may be determined to be available for the turbocharger bearing. In this way, the bearings and shaft hardware are protected from degradation due to premature rotation of the shaft before lubrication oil can be used to protect the hardware. The viscosity of the turbocharger bearing oil may be based on an oil pump pressure that is less than a threshold pressure. An oil pump pressure less than the threshold pressure indicates that the oil viscosity has decreased. In some examples, the oil pump pressure may be based on an output from a pressure sensor of the oil pump. In other examples, turbocharger bearing oil viscosity may be inferred based on the temperature of the engine, where engine temperature may be determined based on ECT or other temperature sensor output.

At 704, a current state of the shaft locking mechanism may be determined. In some examples, the current state of the shaft locking mechanism may be based on a position sensor output of the shaft locking mechanism. For example, if the engine is operating and the rotational speed of the turbocharger shaft is determined to be zero, it may be determined that the shaft locking mechanism is in a locked state. On the other hand, if the engine is operating and the rotational speed of the turbocharger shaft is determined to be greater than zero, the shaft locking mechanism may be determined to be in the unlocked state. In other examples, the current state of the shaft locking mechanism may be based on the last confirmed state of the shaft locking mechanism.

At 706, the current state of the axle locking mechanism may be compared to an expected state of the axle locking mechanism. If the current state of the shaft locking mechanism is the same as the desired state of the shaft locking mechanism, the method may proceed to 710 to maintain the current state of the shaft locking mechanism.

For example, if the desired state of the shaft locking mechanism is a locked state and the current state of the shaft locking mechanism is a locked state, the shaft locking mechanism may remain in the locked state at 710. In other examples, if the desired state of the shaft locking mechanism is an unlocked state and the current state of the shaft locking mechanism is an unlocked state, the shaft locking mechanism may remain in the unlocked state at 710. Similarly, if the desired state of the shaft locking mechanism is a locked state and the current state of the shaft locking mechanism is a locked state, the shaft locking mechanism may remain in the locked state at 710. After step 710, the method may exit at 718.

If the current state of the shaft locking mechanism is different than the desired state of the shaft locking mechanism, the method may proceed to 712 to change the state of the shaft locking mechanism. In other words, if the current state of the shaft locking mechanism is different from the desired state of the shaft locking mechanism, the state of the shaft locking mechanism may change from the current position to the desired position.

For example, if the current state of the shaft locking mechanism is a locked state and the desired state of the shaft locking mechanism is an unlocked state, the shaft locking mechanism may change from the locked state to the unlocked state. In another example, if the current state of the shaft locking mechanism is an unlocked state and the desired state of the shaft locking mechanism is a locked state, the shaft locking mechanism may be changed from the unlocked state to the locked state.

The state of the shaft locking mechanism may be transitioned between the locked state and the unlocked state by positioning a pin of the shaft locking mechanism as described in fig. 5-6.

After changing the state of the shaft locking mechanism at 712, the method may include confirming whether the state of the shaft locking mechanism was successfully changed at 714. In some examples, the change in the state of the shaft locking mechanism may be confirmed to be successful in response to an output of a position sensor of the shaft locking mechanism as described in fig. 5-6.

If the change in state of the shaft locking mechanism at 712 is confirmed to be successful, the method may exit at 718.

If the change in the state of the shaft locking mechanism according to 712 is not successful, the method may include providing an indication of deterioration of the shaft locking mechanism at 720. In some examples, an indication of degradation of the shaft locking mechanism may be provided by illuminating an indicator light. Further, in response to determining an unsuccessful change in the state of the shaft locking mechanism, a mitigating action may be performed at 720. These mitigation actions will be described in more detail in fig. 8. After 720, the method may exit at 718.

Referring now to fig. 8, an example flow diagram of a method 800 for performing mitigating actions for a turbocharger system is shown. In response to determining that the change in the state of the shaft locking mechanism was unsuccessful, method 800 may be performed as part 720 from method 700.

In response to a determination of an unsuccessful change of state at 712, method 800 may begin at 801. At 802, method 800 includes determining whether an axle locking mechanism is stuck (stuck) in a locked state. For example, in response to an unsuccessful transition of the shaft locking mechanism from the locked state to the unlocked state, the shaft locking mechanism may be determined to be stuck in the locked state.

If the shaft locking mechanism is determined to be stuck in a locked state, the wastegate may be opened at 804. In some examples, the wastegate may be fully opened. Opening the wastegate when the shaft locking mechanism is stuck in a locked state may reduce the amount of pressure that the pins of the shaft locking mechanism receive by diverting exhaust gas to bypass the turbine of the turbocharger. Reducing the amount of pressure the pin receives when the shaft locking mechanism is stuck in a locked state may prevent further degradation of the pin. The wastegate may remain in the open position at 804, and method 800 may then end at 812.

At 812, the method may proceed to 718 of method 700 and exit. In some examples, after 804, the wastegate may remain in the open position until the state of the shaft locking mechanism is successfully changed 714.

If the shaft locking mechanism is not stuck in the locked state, it may be determined at 802 that the shaft locking mechanism may be stuck in the unlocked state. In response to determining that the shaft locking mechanism is not stuck in a locked state at 802 (i.e., determining that the shaft locking mechanism is stuck in an unlocked state), the wastegate may be opened at 806.

The desired state of the shaft locking mechanism at 806 is in the locked position since an unsuccessful change of state of the shaft locking mechanism has resulted in the shaft locking mechanism being unable to transition to the locked position at 806. Since the desired state of the shaft locking mechanism is a locked state that inhibits rotation of the turbocharger shaft, and the shaft locking mechanism is stuck in an unlocked state at 806, method 800 may include opening a wastegate. In some examples, the wastegate may be fully open or substantially fully open. Opening the wastegate to a fully open or substantially fully open position when the shaft locking mechanism is stuck in the open position may divert exhaust gas around the turbine of the turbocharger, thereby reducing the rotational speed of the turbocharger shaft. In some examples, inhibiting rotation of the turbocharger shaft may accelerate warm-up of the catalyst and reduce emissions, such as during engine warm-up.

At 808, it is determined whether the temperature of the catalyst is greater than a threshold temperature. In some examples, the threshold temperature may be a light-off temperature of the catalyst. In other examples, the threshold temperature may be a temperature at which the catalyst operates at a desired efficiency. If the temperature of the catalyst is less than the threshold temperature, the method may return to 806 and continue to maintain the wastegate in a fully open or substantially fully open state.

If the temperature of the catalyst is greater than the threshold, the wastegate may be positioned based on a comparison of the desired engine boost and the current engine boost at 810. In some examples, the desired engine boost and the current engine boost condition may be determined based on one or more of a pressure sensor output from a pressure sensor positioned at an inlet of a turbocharger compressor and a turbocharger shaft speed. If the desired engine boost is greater than the current engine boost, the wastegate may be positioned to a smaller open position to increase the amount of exhaust gas that spins the turbine of the turbocharger, thereby increasing the engine boost. In other examples, if the desired engine boost is less than the current engine boost, and the wastegate is not positioned fully open, the wastegate may be positioned in a more open position to reduce the amount of exhaust gas that rotates the turbine of the turbocharger. Positioning the wastegate in a more open position may reduce the amount of exhaust gas that spins the turbine of the turbocharger, thereby reducing engine boost.

The desired engine boost may be based on current engine operating conditions, such as one or more of accelerator pedal position, engine load, and detection of engine knock. For example, the desired engine boost may be increased in response to accelerator pedal fueling, and decreased in response to one or more of accelerator pedal release and brake pedal depression. The amount of desired engine boost may also be increased in response to an increase in engine load, and the desired engine boost may be decreased in response to a decrease in engine load. The desired engine boost may also be reduced in response to detection of engine knock.

In some examples, positioning the wastegate in response to the comparison of the desired engine boost pressure and the current engine boost pressure may include positioning the wastegate in a substantially closed or fully closed position until the desired engine boost pressure demand is met. After the positioning of the waste gate at 810, the method may continue to 812. At 812, method 800 may proceed to 718 of method 700 and exit.

Turning now to FIG. 9, the wastegate position, shaft lock mechanism, turbine speed, temperature of the catalyst (T)_CAT) And a graphical representation 900 of an example relationship between engine speeds.

The graphical representation may correspond to the arrangement shown in fig. 1 and 5-6.

The X-axis of the graphical representation represents time, wherein time is represented on the X-axis arrowIncreasing in the direction of the head. The Y-axis of the top graph represents wastegate position. The Y-axis of the remaining graphs indicates: presence or absence of deterioration of shaft lock device, state of shaft lock device, turbine speed, and temperature (T) of catalyst_CAT) And engine speed.

The wastegate position 902 may be fully open or substantially open at a threshold 912 and may be fully closed or substantially closed at the X-axis of the wastegate position graph.

The shaft lock degradation 904 may be present at the threshold 914 and may not be present at the X-axis of the shaft lock degradation plot.

The shaft lock state 906 may be unlocked at the threshold 916 and may not be present at the X-axis of the shaft lock state graph.

Turbine speed 908 is shown increasing in the same direction as the Y-axis arrow of the turbine speed plot, where turbine speed 908 corresponds to the rotational speed of the turbocharger shaft. The threshold turbine speed 918 may be a rotational speed of the turbocharger shaft used to determine whether to transition the shaft locking mechanism from the unlocked state to the locked state. For example, if the turbine speed 908 exceeds the threshold turbine speed 918, the shaft locking mechanism may not transition to the locked state to avoid damaging pins and/or actuators of the shaft locking mechanism. In another example, if the turbine speed 908 is less than the threshold speed and the desired state of the shaft locking mechanism is a locked state, the shaft locking mechanism may transition to the locked state.

In graphical representation 900, threshold turbine speed 918 is greater than zero. That is, in the graphical representation 900, at the threshold turbine speed 918, the turbocharger shaft is still rotating. However, in other examples, the threshold turbine speed 918 may be zero such that when the shaft locking mechanism transitions to a locked state, the shaft of the turbocharger stops and no longer rotates.

In examples where the threshold turbine speed is zero, rotation of the turbocharger shaft is stopped and no longer rotating, and the risk of damage to the pins of the shaft locking mechanism is reduced compared to examples where the turbocharger shaft may rotate at a high rotational speed.

Temperature (T) of the catalyst_CAT)910 is denoted as being associated with T_CATThe Y-axis arrow of the graph increases in the same direction. Threshold 920 may represent a temperature threshold of the catalyst. In some examples, the temperature threshold may be a light-off temperature of the catalyst. In other examples, the temperature threshold may be a predetermined temperature at which engine warm-up is deemed complete. In other examples, the temperature threshold may be a temperature at which the catalyst operates at a desired efficiency.

The speed of the engine 912 is shown increasing in the same direction as the Y-axis arrow of the engine speed plot.

At time T₀The engine speed may be zero. In response to an engine off condition, the engine speed may be zero. In some examples, at T₀The engine may have been in the off condition for a sufficient period of time since the last engine on condition to allow the temperature 910 of the catalyst to return to about ambient temperature from above the threshold catalyst temperature 920. At T₀The temperature 910 of the catalyst may be less than the threshold temperature 920 of the catalyst. Furthermore, at T₀The wastegate may be closed, the shaft locking means may be active, and the shaft locking means may be in a locked state.

At T₀And T₁In between, the engine speed may increase above zero. The engine speed may be increased in response to a command to transition the engine from an engine-off condition to an engine-on condition. The shaft lock may be at T₁Maintained in the closed position, and the temperature 910 of the catalyst may begin to increase. As engine speed increases, the temperature 910 of the catalyst may increase as exhaust gas flows through the catalyst.

At T₁And T₂In between, the engine speed 912 increases until at T₂Shortly before, and then the engine speed 912 begins to decrease. At T₁Shortly thereafter, the temperature 910 of the catalyst exceeds a catalyst temperature threshold 920. The shaft locking mechanism may transition from the locked state to the unlocked state in response to the temperature 910 of the catalyst exceeding a catalyst temperature threshold 920. Turbine wheelThe machine speed 908 begins to increase after the shaft locking mechanism transitions from the locked state to the unlocked state.

At T₂And T₃Meanwhile, the engine speed 912 continues to drop. In addition, the turbine speed 908 and the temperature 910 of the catalyst begin to decrease. Shaft locking mechanism at T₂And T₃Is maintained in the unlocked state.

At time T₃Engine speed 912 may be zero. For example, in response to a request for an engine off condition, the engine speed 912 may be zero. In response to the engine speed 912 decreasing to zero, the temperature 920 of the catalyst decreases. In addition, the turbine speed 908 also decreases. The shaft locking mechanism state 906 is at T, since the temperature 910 of the catalyst remains above the catalyst temperature threshold 920, and since the turbine speed 908 remains above the threshold turbine speed 918₃Remaining in the unlocked state.

At T₃And T₄In between, the engine speed 912 begins to increase. The engine speed 912 may be increased in response to a request for an engine on condition. The temperature 910 of the catalyst and the turbine speed 908 also increase. The shaft locking mechanism is maintained in an unlocked state.

At T₄And T₅Meanwhile, the engine speed 912 begins to decrease. In addition, the turbine speed 908 and the catalyst temperature 910 also begin to decrease. The shaft locking mechanism is maintained in an unlocked state.

At T₅The engine speed 912 is reduced to zero. The engine speed 912 may be reduced to zero in response to an engine shut-off request.

At T₅And T₆Meanwhile, the engine speed 912 remains at zero. Furthermore, at T₅And T₆In between, the turbine speed 908 decreases below the threshold turbine speed 918 and the temperature 910 of the catalyst decreases below the threshold catalyst temperature 920. The shaft locking mechanism state may transition from the unlocked state to the locked state in response to the temperature 910 of the catalyst decreasing below the catalyst temperature threshold 920 and the turbine speed 908 decreasing below the turbine threshold speed 918. However, in some examples, the temperature 910 of the catalyst is responsive and maySo that the shaft locking mechanism can transition between the locked state and the unlocked state regardless of the turbine speed 908.

At T₆The engine speed 912 begins to increase. In some examples, the engine speed 912 may be increased in response to a request for an engine on condition.

At T₆And T₇Meanwhile, the engine speed 912 continues to increase and the temperature 910 of the catalyst also increases. Further, the shaft locking mechanism is maintained in a locked state, and therefore, the turbine speed 908 remains at zero.

At T₇And T₈In between, the catalyst temperature 910 increases above the catalyst temperature threshold 920. In response to the catalyst temperature 910 increasing above the catalyst temperature threshold 920, the shaft locking mechanism is commanded to transition from the locked state to the unlocked state. However, the change of state of the shaft locking mechanism was not successful; thus, shaft lock degradation is indicated. The wastegate position 902 may be positioned from a closed position to an open position 912.

Positioning the wastegate from the closed position to the open position may prevent additional pressure from being applied to the pin of the shaft locking mechanism when the shaft locking mechanism is stuck in the closed state, and the pin may be in a position to engage the recess of the shaft locking mechanism. At T₈Thereafter, the engine speed 912 decreases and the catalyst temperature 910 also begins to decrease.

Accordingly, a system and method for controlling a turbocharger is provided. A first exemplary system for controlling a turbocharger as described may include: a shaft rotationally coupled to the turbine and a compressor of the turbocharger, and a shaft locking mechanism that inhibits movement of the shaft in response to a first set of engine operating conditions. In some examples, the first set of engine operating conditions may be engine cold start conditions. The shaft locking mechanism may be referred to as being in a locked state when the shaft locking mechanism is in a state of inhibiting movement of the shaft, and may be referred to as being in an unlocked state when the shaft locking mechanism is in a state of enabling movement of the shaft.

A second example of the system optionally includes the first example, and further includes wherein the shaft locking mechanism enables movement of the shaft in response to a second set of engine operating conditions. A third example of the system optionally includes the first example and the second example, and further includes wherein the shaft locking mechanism is a passive shaft locking mechanism. In such examples, the passive shaft locking mechanism may include a phase change material, such as wax, around the shaft and within a recess of the shaft. In some examples, the phase change material may be located between an outer housing and the shaft, where the outer housing is coupled to the shaft and surrounds at least a portion of the shaft. The phase change material of the passive shaft locking mechanism may transition from a solidified state to a liquid state in response to a second set of operating conditions described in the second example of the system, and may enable movement of the shaft once the phase change material has transitioned from the solidified state to the liquid state. Further, the passive shaft locking mechanism may inhibit movement of the shaft via solidification of the phase change material. In other words, the phase change material of the shaft locking mechanism inhibits movement of the shaft when it is in a solidified state.

In a fourth example that optionally includes the shaft locking mechanism of the first example, the shaft locking mechanism may be an active shaft locking mechanism. In such examples where the shaft locking mechanism is an active shaft locking mechanism, the active shaft locking mechanism may include a pin that fits within a slot of the shaft. A pin of the active shaft locking mechanism may be positioned within a slot of the shaft to inhibit movement of the shaft.

In a first example of a method, movement of a shaft of a turbocharger may be inhibited via a shaft locking mechanism in response to an engine cold start condition. A second example of the method optionally includes the first example, and further includes enabling the shaft to move even during a cold start condition of the engine if the turbine inlet pressure is greater than a threshold pressure. In response to the inlet pressure being greater than the threshold pressure, enabling movement of the shaft even during a cold start condition of the engine may prevent damage to the shaft locking mechanism. In some examples, the turbine may be enabled to move even during a cold start condition of the engine, for example, in response to any one or more of the override conditions discussed with respect to fig. 7.

A third example of a method optionally including the first example method and the second example method further comprises: the shaft is enabled to move in response to a second set of engine operating conditions. The second set of engine operating conditions may include one or more of a viscosity of turbocharger bearing oil less than a threshold viscosity and a catalyst temperature greater than a threshold temperature. However, the second set of engine operating conditions may include any one or more of the conditions indicating completion of engine warm-up as discussed with respect to FIG. 7.

A fourth example of the method optionally includes one or more of the first example method through the third example method, and further includes adjusting the wastegate position in response to degradation of the shaft locking mechanism. Adjusting the position of the wastegate in response to degradation of the shaft locking mechanism may be beneficial to prevent damage to the shaft locking mechanism and to meet engine operation requests (e.g., desired boost). Degradation of the shaft locking mechanism may include the shaft locking mechanism being stuck in a locked state. In other examples, degradation of the shaft locking mechanism may include the shaft locking mechanism being stuck in an unlocked state.

A fifth example of the method optionally includes one or more of the first example method through the fourth example method, and further includes adjusting the wastegate to the open position in response to the shaft locking mechanism being stuck in the locked state. In some examples, the wastegate may be fully open or substantially fully open. However, in other examples, the wastegate may only be opened sufficiently to reduce the pressure placed on the shaft locking mechanism to less than the threshold pressure. By reducing the amount of exhaust gas flowing through the turbine of the turbocharger, opening the wastegate may avoid or reduce damage to the shaft lock mechanism, thereby reducing the amount of pressure placed on the shaft lock mechanism that is stuck in a locked state. In some examples, the wastegate may remain in the open position when the shaft locking mechanism is stuck in the locked state until the shaft locking mechanism is determined to no longer be stuck in the locked state.

A sixth example of the method optionally includes one or more of the first through fifth example methods, and further includes adjusting the wastegate to the open position in response to the shaft locking mechanism being stuck in the unlocked condition until a temperature of the catalyst is greater than a threshold temperature. By reducing swirl and thus residence time of exhaust gases in the exhaust system before the exhaust gases reach the catalyst, this may be beneficial to accelerate catalyst light-off even if the shaft locking mechanism is unable to prevent rotation of the turbocharger.

A seventh example of the method optionally includes one or more of the first through sixth example methods, and further comprising: if the shaft locking mechanism is stuck in the unlocked state and the catalyst is greater than the threshold temperature, the wastegate is positioned in response to a comparison of the desired engine boost pressure and the current engine boost pressure. If the seventh example of the method includes the sixth example of the method, in the seventh example method, the positioning of the wastegate is to reposition the wastegate from an open position (e.g., a fully open or substantially fully open position) to a position responsive to a comparison of the desired engine boost pressure and the current engine boost pressure. Positioning the wastegate in response to a comparison of the desired engine boost pressure and the current engine boost pressure may be beneficial to meet engine operating requirements when the shaft locking mechanism is stuck in an open state (open) and the catalyst is greater than a threshold temperature. For example, the threshold temperature of the catalyst may be a light-off temperature of the catalyst or a temperature at which the catalyst operates at a desired efficiency.

It should be noted that the example control and estimation routines included herein may be used with various engine and/or vehicle system configurations. The control methods and programs disclosed herein may be stored as executable instructions in non-transitory memory and executed by a control system that includes a controller in combination with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and/or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the described acts are performed by executing instructions in the system comprising various combinations of engine hardware components and electronic controllers.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above-described techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

1. A turbocharger system, comprising:

a shaft rotationally coupled to the turbine and the compressor; and

a shaft locking mechanism that inhibits movement of the shaft in response to an engine cold start condition,

wherein the shaft locking mechanism is a passive shaft locking mechanism, and wherein the passive shaft locking mechanism comprises a phase change material surrounding the shaft and within a recess of the shaft.

2. The system of claim 1, wherein the passive shaft locking mechanism inhibits motion of the shaft via solidification of the phase change material.

3. A method for accelerating catalyst light-off, comprising:

inhibiting, via a shaft locking mechanism, movement of a shaft of a turbocharger coupled to a turbine rotor positioned in an exhaust stream of an engine in response to a first set of engine operating conditions including a cold start condition of the engine; and

enabling movement of the shaft if turbine inlet pressure is greater than a threshold pressure, even during the cold start condition of the engine.

4. The method of claim 3, further comprising enabling movement of the shaft in response to a second set of engine operating conditions.

5. The method of claim 4, wherein the second set of engine operating conditions includes a viscosity of turbocharger bearing oil less than a threshold viscosity.

6. The method of claim 4, wherein the second set of engine operating conditions includes a catalyst temperature greater than a threshold temperature.

7. The method of claim 3, further comprising adjusting a wastegate position in response to degradation of the shaft locking mechanism.

8. The method of claim 7, wherein the degradation of the shaft locking mechanism comprises the shaft locking mechanism being stuck in a locked state, and wherein the wastegate is adjusted to an open position in response to the shaft locking mechanism being stuck in the locked state.

9. The method of claim 7, wherein the degradation of the shaft locking mechanism includes the shaft locking mechanism being stuck in an unlocked state, and wherein the wastegate is adjusted to an open position until a catalyst temperature is greater than a threshold temperature in response to the shaft locking mechanism being stuck in the unlocked state.

10. The method of claim 9, further comprising positioning the wastegate in response to a comparison of a desired engine boost pressure and a current engine boost pressure when the shaft locking mechanism is stuck in the unlocked state and the catalyst is greater than the threshold temperature.

11. A turbocharger system, comprising:

a shaft rotationally coupled to the turbine rotor and the compressor rotor; and

a shaft locking mechanism that inhibits movement of the shaft in response to a first set of engine operating conditions and enables movement of the shaft in response to a second set of operating conditions, wherein the first set of engine operating conditions includes an engine cold start condition,

wherein the shaft locking mechanism is passively controlled, and wherein the phase change material of the shaft locking mechanism inhibits movement of the shaft when in a solidified state.

12. The system of claim 11, wherein the phase change material surrounds the shaft and is located within a recess of the shaft.

13. The system of claim 12, wherein the phase change material transitions from the solidified state to a liquid state in response to the second set of operating conditions.